USPTO Patents Application 09888458

PHDE000090

11.04.2001

Microcontroller

The invention relates to a microcontroller comprising a command decoder.

Single-chip microcomputers which are generally used for controlling
apparatuses and in which CPU, memories and ports are integrated on a chip are understood to
be microcontrollers. The CPU comprises in known manner a command decoder which
decodes the loaded commands and performs a run-off control in order that the commands are
carried out by the computer.

Microcontrollers are programmed in a machine-dependent assembler
language. In the known assembler languages, all assembler commands, with the exception of
the conditional program steps, are executed independently of data. When different operations
must be performed in dependence upon given data, this is possible in conventional
microcontrollers only wdth a considerable programming effort. The condition to be realized
must then be extensively encoded in the assembler. When, for example, generic pointers in a
high-level language compiler are to be programmed by means of different assembler
commands dependent on the addressed memory, this requires a high programming effort or,
by substitution, a considerable number of hardware components for reconfiguring the
memory.

Based on this background, it is an object of the present invention to improve a
microcontroller of the type described in the opening paragraph as regards its functionality
and to simplify the programming.

This object is achieved by a microcontroller as defined in the characterizing
part of claim 1 . Advantageous embodiments are defined in the dependent claims.

The microcontroller comprises a command decoder as well as at least one
memory to which the command decoder has direct access. The command decoder is adapted
to decode at least one conditional command, the result of the decoding of the conditional
command depending on the contents of the memory to which the decoder has access. When
the command decoder thus loads a conditional command, it checks the contents of the
memory to which it has access and, in dependence upon the result of this check, it supplies a
machine command from a series of possible machine commands, which are associated with

PHDE000090

2 11.04.2001
the loaded conditional command, to the computer. The memory, to which the microcontroller
has access, may be particularly a register which is present on the microcontroller.

Due to its mode of operation, the microcontroller according to the invention
allows a considerably greater flexibility in its use and in programming without extensive
changes in the structure of the hardware being necessary. A conditional command can be
used for programming in the same way as conventional assembler commands. When
executing the program code, it ensures a greater flexibility because the actually performed
instruction depends on the data which are present at the instant of forming this instmction in
the memory to which the command decoder has access.

The memory, to which the command decoder has access, is preferably adapted
in such a way that it can comprise input data of the microcontroller. Input data of the
microcontroller may be particularly digital or digitized information supplied by a cormected
apparatus.

In accordance with a special embodiment of the invention, the command
decoder is adapted in such a way that, dependent on the contents of the memory to which the
command decoder has access, the conditional command is decoded as an access command
for the computer to different memory types. The access to different memory types, starting
from the same conditional command, is a frequently occurring situation of use in which the
embodiment of the microcontroller according to the invention is particularly advantageous.
Numerous microcontrollers have different assembler commands for access to different
memories. For example, the microcontroller 80C51 has the command "mov" for moving data
memory data and the command "move" for code memory data. A generic pointer (for
example in the high-level language C) which has address-controlled access to the overall
implemented memory is possible for such microcontrollers with either considerable
assembler code effort or with additional hardware-supported memory configurations
(memory mapping). In contrast, the implementation of a data-controlled, conditional
command with a single program command allows access to all implemented data memories,
because the relevant desired instruction is decoded in dependence upon the data, for example,
dependent on the contents of a processor register as a pointer. This operation has the external
effect of access to a linear memory. It is therefore a great advantage that, for example,
memory management imits which are provided can be used without any change in spite of
virtual reconfiguration of the memory.

PHDE000090

3 11.04.2001
The sole Figure diagrammatically shows the elements of a microcontroller 100
according to the invention.

f !

5 The Figure only shows the arithmetic-logic unit ALU 12 and the command

decoder 15 as logic components of the microcontroller 100 shown in a very simplified form.
The ALU 12 and the command decoder 1 5 are connected to a common bus 1 3 to which the
inputs 10 and outputs 1 1 of the microcontroller are also connected. The conmiand decoder 15
further has a direct connection 16 with the ALU 12 via which the run-off control is
1 0 performed.

According to the invention, the conmiand decoder 1 5 has direct access to a
memory 14 which may be, for example, a register of the microcontroller. Data of different
origin, for example, data from an input 10 of the microcontroller, may be loaded into the
m memory 14.

if 1 5 The command decoder 1 5 is adapted in such a way that it can perform

^ conditional commands. In the case of a conditional command, the command decoder 15

Lri

m selects one out of a plurality of associated machine commands in dependence upon the

L contents of the memory 14 and supplies this command to the ALU 12. For example, the

yl command decoder may supply the command mov or the command move to the ALU in

20 dependence on the contents of the memory 14. However, in both cases, the starting point is
the same conditional assembler command so that a distinction in this respect is not required
during programming. The microcontroller according to the invention thus provides the
possibility of considerably reducing the progranmiing effort so that both the system
performance and the code density can be significantly increased with a small mmiber of
25 additional hardware components.
Reference numerals:

30

100

microcontroller

10

input connection

11

output connection

12

computer

13

bus

14

memory

15

command decoder

16

connection